Conventional technology exists for displaying a traffic condition so that the traffic condition can be understood visually.
For example, technology has been proposed in which traffic condition evaluations from respective observation points based on vehicle speed and the number of passing vehicles are displayed as marks at positions corresponding to the actual observation points on a road map. In such technology, the displayed marks are displayed with display attributes (color and blinking) that accord with the traffic condition evaluations of the corresponding observation points.
Moreover, technology has been proposed in which map data read from a map data storage unit is, for example, divided by plural meshes, and for each mesh, evaluation values indicating an extent of congestion on roads are computed and the roads are displayed with color coding.